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post #1 of 19 (permalink) Old 06-26-2011, 09:39 AM Thread Starter
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Weird Electrical Problem

A few weeks ago I went to start the car and it was dead, no power to anything, no lights etc. My friend jumped it and it started right up. I went straight to Autozone and had them test the battery and it was fine. Since there's no way it could have fully charged by running for 15 minutes I knew something wasn't right.

It happened at Tim's again last week when he changed my upper control arms but all he did was disconnect the pos terminal, reconnect it and the power was there. Today I was changing my headlight sockets and had to run to Radio Shack, I was on my way back and went around a turn into the neighborhood and it just died. Same thing, no power to anything. I got out, disconnected the pos terminal, let it sit for a few seconds, put it back on and power is back again. It had done this a few times a few years ago and I took it to a shop and they said my battery cables were rotted all the way through. They replaced the cables and the problem went away for the last 2 years or so and is just now resurfacing.

It sounds like the issue Gunn had but my power doesn't come on when the key is turned on then go black when you crank it. I get no power at all unless I disconnect the battery terminal and reconnect it. Today was a little spooky since it literally died in a turn and has never done that before and I was planning on heading back to Utah in a few days (700 miles through a lot of mountains). I don't really want to chance it happening at 75mph. We also just did the Big 3 and the terminals are tight and clean.

I found a few old posts and I'm thinking maybe the ignition switch in the steering column is loose or broken since I can't think of anything else that would literally cut all power from the car then come back when you disconnect/reconnect the battery cable. The positive cable is only about 2-3 years old but I'll check that too if it's not the ignition switch. I was wondering too if a shorting starter relay could do that, cut all power to the car. It's going to be hot today (112) and I want to make sure I'm checking the right areas.

-Kelly
===================================
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90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
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post #2 of 19 (permalink) Old 06-26-2011, 10:28 AM
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Usually, something like that would be a bad cable around the battery and alternator circuit.

I'd triple-check for corrosion on both ends of both.

Also, check your ignition switch - if you can swap a loaner in, that's ideal. New should be under $50 or so.

Of course, when I bought Ruby Jean, I laid a visual on it - the darn thing was in two pieces (!!!) so it was pretty obvious what was wrong with it

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post #3 of 19 (permalink) Old 06-26-2011, 10:45 AM
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No Lights? Would seem to rule out ign sw. Did your radio presets drop out before you disconnected anything?

This calls for a test light. Happens again, turn lights on, test first between bat pos post and frame, then between Bat neg post and frame. If test light on when neg post tested, bad ground.. more common than you would think. Remember, the neg/ground side needs clean direct connections to chassis AND block AND ALSO firewall to block strap. Check and make sure all connections are clean and tight. BTW, tight and grease with no corrosion is a good thing. Keeps corrosion away.

Also, WIGGLE and TUG test is a proper accepted way to find bad connections. Even for pros.
It's rare but I once had a battery with a bad internal connection.

Last edited by pettyfog; 06-26-2011 at 10:53 AM.
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post #4 of 19 (permalink) Old 06-26-2011, 11:43 AM Thread Starter
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Yea even though the regular battery cables are fairly new I've heard of them being defective. I have a multimeter but it's not a really nice one. I'll try the tests if/when it does it again. I had no lights, no door chime so maybe not the ignition switch but it can't hurt to check it.

I have all of this so I doubt it's the ground,
http://forums.tccoa.com/showpost.php...5&postcount=73
(Edit: it was doing this before adding the Big 3)

It just has me stumped so far since it's random and when it happens I have zero power anywhere but resets by simply unhooking the battery. I would think no power at all would be the + wire going into the mega fuse block but no juice to the starter either. I may cut the terminal off and put a different one on.

-Kelly
===================================
Fuelly
94 LX 3.8L NA : Daily Driver. 270k on chassis, 10k on motor.
90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
WTB: 90 SC BHJ harmonic balancer
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post #5 of 19 (permalink) Old 06-26-2011, 11:57 AM
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I'll add that maybe you have a bad battery, and when you disconnect/reconnect you're reconnecting INSIDE the battery by the movement.

Dunno for sure - only way I know to test would be to carry the meter with you and when it's dead, turn the lights on (so you can see if it lights back up) and probe the two posts on the battery.

RwP
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post #6 of 19 (permalink) Old 06-26-2011, 12:21 PM
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Quote:
Originally Posted by BlueEyes View Post
It just has me stumped so far since it's random and when it happens I have zero power anywhere but resets by simply unhooking the battery. I would think no power at all would be the + wire going into the mega fuse block but no juice to the starter either. I may cut the terminal off and put a different one on.
I'd hook a wire to the starter + wire, right at the starter. Insulate it well, and run it up near the battery, and tape it off so it can't short.

Next time it acts up:

Measure the wire added above to ground at the battery terminal. If it measures ~12V, try to start the car, and see what the voltage does.

If it stays at 12v, it's not the wire to the starter, or to the supply side of the megafuse.

Measure the other side of the megafuse, trying not to disturb the wires. If it's not reading the same, it's bad. Adding another wire here for the meter can help.

Then we have the fusebox; but all your problems seem to be everything, and that pretty much ends at the megafuse, for the supply side...

Otherwise, it's going to be ground wires; read the big three article, and go from there.

Be sure to disconnect any wires added for diagnosis. It much easier to add a piece of wire in the driveway, rather than crawling in the mud to wiggle a wire, lol.

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post #7 of 19 (permalink) Old 06-26-2011, 12:50 PM Thread Starter
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Thanks for the tips Ralph, Pettyfog and Grog. I'll give these a shot. Since it is a no-power situation I was pretty sure it was right near the battery and if the wires test out fine maybe the battery itself.

I forgot to mention the reason why at first I thought it was the ignition switch was a few times the lights did come on (idiot lights) but no crank. But now seems to have gotten worse with the no power at all mode.

I do have the Big 3 setup with 0 gauge wire and everything is connected tight. That was the first thing I checked but like I said it was happening before all that was added.

I'll see if maybe I can hook up the extra wire to the starter but don't think I can, I'm in a wheelchair and can't really crawl under my car but you guys gave me some good starting points and I'll test what I can next time it happens.

When we added the Big 3 the alt was testing fine so possibly the fuse is bad. I would think if it was solely the battery it wouldn't have died while it was running, the alt would have kept it running.

-Kelly
===================================
Fuelly
94 LX 3.8L NA : Daily Driver. 270k on chassis, 10k on motor.
90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
WTB: 90 SC BHJ harmonic balancer

Last edited by BlueEyes; 06-26-2011 at 05:44 PM.
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post #8 of 19 (permalink) Old 06-26-2011, 01:33 PM
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The wire that goes to the starter is near the battery, below the fuse box there is a single solid black wire with a connector.

Sounds like a bad connection somewhere on the main power circuit. I have a bad connection at the battery on my Super coupe .. if the battery terminal is a little loose, you try o start it and it just kills the whole car - play with the terminal a bit, and it starts right up.

Had another 4.6 Tbird which would do the same thing - power would just kill and it turned out to be bad MLPS. We verified this without having to go under the car by doing some testing at the connector where the transmission connects to the dash wiring - right below the radio area, there is a White connector you can probe to determine if the Neutral Safety starting circuit ( to the MLPS ) is not operating correctly when you have a NO start condition.
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post #9 of 19 (permalink) Old 06-26-2011, 05:52 PM Thread Starter
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Well of course it didn't do it today but I have the multimeter in the car. it's starting to make a little more sense the more I think about it. Remember I also had the sporadic random downshifting issue so when it happens again will check the plug you mentioned, half of my dash is out so I can see the plug sitting there. if it doesn't do it again today I'm just going to do the MLPS testing since I can do it from inside the car.

-Kelly
===================================
Fuelly
94 LX 3.8L NA : Daily Driver. 270k on chassis, 10k on motor.
90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
WTB: 90 SC BHJ harmonic balancer
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post #10 of 19 (permalink) Old 06-29-2011, 11:24 AM Thread Starter
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Well it still hasn't died again. Yesterday I did notice a loose wire coming out of the megafuse block, I think it's the wire that goes to the starter. It was so hot outside I couldn't lean on the car to get a good look. I wish I had a garage to work in. It looks like when they added the fog lights they tapped into the power right there but I'm heading out to look at it right now to make sure.

Still need to get under the car to test the VSS & MLPS, I think I may have a few problems happening all at once that is causing the no power problem and won't know for sure until I get everything checked out.

-Kelly
===================================
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94 LX 3.8L NA : Daily Driver. 270k on chassis, 10k on motor.
90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
WTB: 90 SC BHJ harmonic balancer
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post #11 of 19 (permalink) Old 06-30-2011, 06:33 PM Thread Starter
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Well it still hasn't done the no power thing again and I've been driving it every day. This morning I was able to check out a few things before it hit 115 again.

When they put my fog lights in they thought it would be a good idea to tap into the power right at the high amp fuse box and the nut was a little loose holding down the wire to the starter. I took the steering wheel cowl off and the ignition switch is tight, looks almost brand new actually. No corrosion on the terminals. I also noticed that when we did the Big 3, the pos terminal shape doesn't allow all of the terminals from my stereo power, alt and power to the high amp fuse box to stack flat even with the bolt tightened down so there are some gaps there. I need to go grab a different terminal and make sure they are all in there tight.

I got some 12,000lb. gvw ramps ( I had read that the 8,000's were a little flimsy) so tomorrow I can actually get under the car to test things. I checked the schematics and although I can see that connector just inside the dash near the center console I can't find it in the book so I'm not sure what wires to test. I'll have to look again but if I can't find it I'll have to get under the car. I wanted to check the harness anyway and test the VSS.

-Kelly
===================================
Fuelly
94 LX 3.8L NA : Daily Driver. 270k on chassis, 10k on motor.
90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
WTB: 90 SC BHJ harmonic balancer
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post #12 of 19 (permalink) Old 07-01-2011, 12:02 PM
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I'm pretty dang sure you'll find the problem under the hood, not in the cabin. I think you hit on it there with the connection near the box. Also check all three major ground points just to be safe.
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post #13 of 19 (permalink) Old 07-01-2011, 03:19 PM Thread Starter
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Even with the ramps I couldn't get to the MLPS. Well I can get to it but can't move around or get my hands in there to do any testing, the car needs to be higher. The trans harness plug was totally caked with grease so I cleaned it up as best I could but need to take it somewhere since I can't get it any higher off the ground myself.

The reason for testing from inside is the harness that goes from the MLPS to the PCM has a connector you can get to from inside the car instead of getting under it.

Anyway I need to get the fluid and filter changed in the trans so I'll take it down there Tuesday and have them test the other things just for peace of mind.

-Kelly
===================================
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94 LX 3.8L NA : Daily Driver. 270k on chassis, 10k on motor.
90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
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post #14 of 19 (permalink) Old 07-01-2011, 03:54 PM
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The Gray / Red wire is the Signal return to the PCM ... it ties the OSS (output shaft sensor) and the MLPS together. The MLPS is a series of resistors, so depending on what gear you put it in, it will have different voltage reaadings back to the PCM on the Light blue / Yellow wire.

Usually if you want to test a component, it needs to be disconnected from everything else - either at the MLPS sensor itself, you can check resistance in the circuit .. ( testing procedues on 149-6 of the 94 EVTM ) or with the connector by the transmission tunnel disconnected

Starter relay circuit is the White/Pink and the Red/Light blue if you want to check for voltage during a NO start condition.
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post #15 of 19 (permalink) Old 07-01-2011, 05:13 PM Thread Starter
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With the MLPS you have to check the resistance in each gear so really you have to test it in the car but still I just cant get in there to do anything. Not enough room.

-Kelly
===================================
Fuelly
94 LX 3.8L NA : Daily Driver. 270k on chassis, 10k on motor.
90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
WTB: 90 SC BHJ harmonic balancer
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post #16 of 19 (permalink) Old 07-01-2011, 05:47 PM
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Quote:
Originally Posted by BlueEyes View Post
With the MLPS you have to check the resistance in each gear so really you have to test it in the car but still I just cant get in there to do anything. Not enough room.
The connector at the trans tunnel is a little further back ... if you remove the center console lower half completely you should have a little more room.
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post #17 of 19 (permalink) Old 07-01-2011, 06:27 PM Thread Starter
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Yea I meant no room from underneath the car. The connector in the dash is a wide flat white connector right? I'll look at it tomorrow, it's way too hot to be outside now. Going to be 116+ tomorrow so my best bet for working on the car is to get out there at 4:30-5am. I have the diagrams and the trouble shooting charts with the resistances. But even if it tests bad I can't get to it under the car to change it.

I only know one guy who has a shop who would let me just roll in and put it up on the lift and work on it myself but I used to work for him and left kind of on bad terms.

I think it sucks that I didn't have room with the ramps. Maybe if I put the rear tires on them.

Anyway I need to have it checked out what ever I can't do over the weekend. Too many wasted days with no results and I need to get home.

-Kelly
===================================
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90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
WTB: 90 SC BHJ harmonic balancer
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post #18 of 19 (permalink) Old 07-01-2011, 07:12 PM
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I had a similar problem a few weeks ago, though never lost memory on anything. Turned out to be the ABS fuse (under the hood) arcing and screwing with the IGN fuse/circuit. ABS fuse blew, noticed oxidized fuse connector (screw) replace with new fuse and all has been fine since.

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post #19 of 19 (permalink) Old 07-01-2011, 07:19 PM Thread Starter
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I checked the fuses and they look ok but yes I've heard of them blowing but would work intermittently. It's a possibility.

I just need to figure it out. If the car dies when I'm going 75 mph on the interstate that could be trouble.

-Kelly
===================================
Fuelly
94 LX 3.8L NA : Daily Driver. 270k on chassis, 10k on motor.
90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
WTB: 90 SC BHJ harmonic balancer
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